Axial flow fans are used in a wide range of air-conditioning devices, ventilation devices, and the like, and reduction of noise of the axial flow fan is demanded. There have been proposed a variety of axial flow fans devised to reduce noise. As such an axial flow fan, there is one disclosed in which “an axial flow fan comprising a plurality of blades disposed at an outer periphery of a cylindrical boss portion, wherein a shape of each of the blades is defined such that, in any portion of a section of the blade along a given plane radially extending from a rotation centerline through a blade root portion contacting the boss portion, the blade is bent toward an outer peripheral portion side, the outer peripheral portion of the blade is directed in an air sending direction, and a horizontal angle of the blade gradually increases as the blade extends toward the outer peripheral portion side” (for example, see Patent Literature 1).
In the axial flow fan described in Patent Literature 1, in addition to the above-described structure, each blade is formed as a swept-forward wing, and a swept-forward angle formed between a line connecting the rotation centerline and the midpoint of the blade root portion and a line connecting the rotation centerline and the midpoint of an outer peripheral edge of the blade is set to an angle in a range from 20° to 40°, thereby reducing noise.